As the optic and electronic technologies advance, backlight devices are continuously developed in various applications in life, for example, projectors and LCD displays. Nowadays, head up displays (HUDs) for vehicles are developed and applied extensively to assist drivers. With them, a driver doesn't need to bow his head to view the dashboard. Instead, the important driving information can be seen in the normal visual field. By reducing the frequency of checking the dashboard, the interruption of attention can be avoided, and the control of the status and consciousness will not be lost. Consequently, the driving safety can be improved. HUDs can integrate and replace various traditional dashboards such as speedometers, fuel meters, and status indicators. Normal HUDs require backlight devices before images can be displayed.
In general, backlight devices and HUDs have to share a limited space for providing optical images. Unfortunately, normal backlight device requires larger space for optical reflection, which makes the overall size increase. Besides, the heat dissipation structure of backlight devices also occupies greater space. In addition to increasing the manufacturing costs, once the size is too large, it is difficult to design HUD products into vehicles. Accordingly, size, costs, and design convenience are still the challenges for manufacturers.
To sum up, to solve the technical drawbacks as described above, the present invention provides a backlight device. By using a plurality of light sources incident to a plurality of optical devices, the optical space needed by the light sources can be distributed and hence reducing the overall size of the structure. Thereby, the equipment costs can be lowered, and the design convenience can be enhanced. In addition, a preferred dissipation structure can be provided to a limited space.